Method of producing small crates or other plastic receptacles by assembling sections with extruded profiles

ABSTRACT

A method is provided for producing plastic containers such as crates by assembling two shaped sections (7) forming opposite ends (5d and 5e) of the container along with a shaped section (1) forming the sides (5b and 5c) and the bottom (5a) thereof. Said shaped sections (7 and 1) are obtained by extruding, punching and cutting plastic material.

The present invention concerns a method to series produce a plasticreceptacle with the overall shape of a parallelpiped and able to be usedas a small crate for the handling, packaging and transportation ofagricultural products, such as fruit or vegetables.

There currently exist several types of crates with variable dimensionsand composed of diverse materials, such as wood, cardboard or plasticmaterials, such as vinyl polychloride, polyethylene, polypropylene andexpanded polystyrene, all these materials being cited as examples.Crates made of wood or cardboard have on usage two major drawbacks. Thefirst one is their permeability to water which firstly significantlyreduces the mechanical resistance of the crates and secondlyconsiderably alters the weight of the tare constituting said crates. Thesecond drawback resides in the fact of their inflammability and therisks inherent of this characteristic concerning storage, whether thecrates be empty or full. So as to mitigate these drawbacks, users wouldlike to be able to replace cardboard or wooden crates with impermeableplastic and preferably non-inflammable crates. However, existing plasticcrates do have the drawback of being much more expensive than wooden orcardboard crates. It is well-known that this extra cost is due far lessto the cost of the plastic material than to its transformation into afinished product. In fact, plastic material transformation methods usedto industrially produce crates or similar shaped receptacles arecurrently thermoforming, pressing-moulding or via injection androtational plastic moulding, that is methods with discontinuousproduction requiring a long expensive production time. The purpose ofthe present invention is to overcome this drawback by reducing the costof transformation of the plastic material into a finished product intothe form of a crate or other receptacle. The principle retained toreduce this transformation cost is to significantly increase theproduction flowrate of crates or other receptacles by using thecontinuous transformation method of the plastic materials represented byextrusion, said method requiring with equal productivity an investmentin machines and tools significantly lower than that for machines andtools used in the above-mentioned discontinuous transformation methodsand in particular for producing a large number of plastic crates orother plastic receptacles.

The present invention concerns a method to produce plastic crates orother plastic receptacles at a high flowrate by mounting, possiblyautomated, of two or several types of perforated or truncated extrudedprofiles with suitable shapes and mechanical properties.

The present invention shall be more readily understood on reading therelevant details of the following description with reference to figuresof the attached diagrams, namely:

FIG. 1 shows an overall view of the plastic crate or receptacle 5 to beproduced and which comprises a bottom 5a and four sides 5b, 5c, 5d and5e,

FIG. 2 shows the shape the profile may assume with one section 1intended to form the bottom 5a and two opposing sides 5b and 5c of theplastic crate or receptacle 5,

FIG. 3 shows the shape the profile may assume with two sections 1a and1b intended to form the bottom 5a and two opposing sides 5b and 5c ofthe plastic crate or receptacle,

FIG. 4 shows the shape the profile 3 may assume with two sectionsintended to form the two sides 5d and 5e of the plastic crate orreceptacle 5.

FIG. 5 shows a perforation example 4 of the surface of any one of thesides 5b and 5c or of the bottom 5a of the plastic crate or receptacle 5to be produced,

FIG. 6 shows another perforation example 6 of the surface of any one ofthe sides 5b and 5c or the bottom 5a of the plastic crate or receptacleto be produced.

FIG. 7 shows a perforation example of any one of the sides 5d and 5e ofthe plastic crate or receptacle to be produced,

FIG. 8 shows one particular detail of a border 7a of the profile 7 andthe possibility to use a pile-up pin 12.

As shown on FIG. 2 and according to a particular main embodiment, aprofile section 1, produced by the extrusion of a plastic materialthrough a die and a device to produce the appropriate shapes, has aU-shaped cross section whose two branches forming the lateral sides 5band 5c are perpendicular to the side forming the bottom 5a. Said lateralsides 5b and 5c and said bottom 5a may comprise on their two faces, orsolely on one face, longitudinal reinforcing grooves 2 or longitudinalreinforcing ribs 3, or even a combination of said grooves and ribs. Thelength of the profile section 1 represents the total length of theplastic crate or receptacle 5 to be produced, this length possibly being60 cm.

Alternatively, the bottom 5a and the lateral sides 5b, 5c may beobtained from a flat extruded profile folded along two longitudinalgrooves.

In one example of a secondary embodiment shown on FIG. 3, the profilesection 1 may be constituted by the longitudinal juxtaposition of atleast two sections 1a and 1b, said sections 1a and 1b being able to beassembled, for example, via the longitudinal sliding of one into theother or by one being clipped into the other. Should the elements of thecrate or receptacle need to be transported to a distant assembly site,this secondary embodiment has the advantage of reducing the cost of saidtransport by limiting the transported volume for a given number ofcrates or receptacles. In fact, the stacking of L-shaped profiles, suchas that of the sections 1a and 1b, allows less empty spaces than wouldbe the case with the stacking of U-shaped profiles, such as the profilesection 1.

Once the profile section 1 described in the main embodiment has beenextruded and significantly cooled, its surface is then perforated so asto firstly lighten the finished product, secondly reduce the cost ofproduction by recycling the material fragments produced by thisperforation and thirdly significantly increase the rigidity of the sides5a, 5b and 5c. The increasing of the rigidity of the sides 5a, 5b and 5cmentioned above derives from the stretching of the material carried outduring perforation at the periphery of the perforated orifice and whichinduces a traction prestressing in said sides. FIG. 5 shows the detailsof a perforation example 4 perforated by a punch with a circular sectionand reveals a stretching cone 4a which contributes in stiffening theperforated side. There are many perforation shapes enabling these aimsto be achieved and a judicious choice of the drawing represented by thecontour of certain perforations may provide the latter with anadditional role in representing a brand image or original indication. Byway of a non-restrictive example shown on FIG. 6, perforations 6 formingthe silhouettes of Corsica on the sides of a crate of citrus fruits maycontribute in promoting the products from this island.

The sides 5d and 5e of the plastic receptacle or crate are each producedby extrusion, the perforation and sectioning of a profile 7 being shownon FIG. 4. Said profile section 7 is longitudinally limited by twohollow borders 7a and 7b with a preferably triangular section butpossibly rectangular or comprising a curved side. The faces of thisprofile section 7 may be provided with longitudinal stiffening ribs orgrooves similar to the grooves 2 and the ribs 3 described earlier. Theborders 7a and 7b are intended to firstly allow for a linking of thesides 5d and 5e with the sides 5b and 5c by an assembling device to bedescribed subsequently, and secondly to support the vertical gravimetricload resulting from the stacking of the crates or receptacles. By way ofexample, the gravimetric load to be supported for the lower crate in astacking of eleven crates filled with citrus fruits is about 120 kg. Thelength of the profile section 7 represents the height of the sides 5dand 5e of the plastic crate or receptacle to be produced; this lengthmay be 17 cm. According to one particular embodiment of the invention,described hereafter with details illustrated on FIG. 8, anotheradvantageous characteristic may be conferred on the plastic crate orreceptacle by virtue of the use of four borders 7a or 7b which theplastic crate or receptacle comprises. It merely suffices to provide aperforation 10 on one or several of the portions of the bottom 5aintended to coincide with one or several of the border sections 7a or 7bso that one or several of the borders 7a or 7b enable a pin 12 to slideinto their hollow portion 11, which then serves as a sheath, said pin 12constituted by a profile with a appropriate section, said profilepossibly being obtained by the extrusion of a rigid plastic material.The pin 12 is intended to allow for and maintain a vertical alignment ofthe stacked crates at the time they are stored and transported. Thelength of the pin 12 is preferably greater than the height of one crateand smaller than the height of two stacked crates for reasons of alimited small spatial requirement and so as to enable the upper crate tobe taken from a pile whilst keeping the lower stacking aligned. However,this pin height may also be much greater than the height of two stackedcrates.

Once the profile 7 has been extruded and significantly cooled, itssurface is subjected to two types of perforations, the first type beingsimilar to the one described on the profile section 1, the second typebeing specific to said profile 7 and made so as to provide spaces in thesides 5d and 5e said profile is to constitute, said spaces allowing formanual taking as regards the handling of the plastic crates orreceptacles. One non-restrictive example of such a perforation is shownon FIG. 7. A perforated opening 8 allows for the passage of at leastfour fingers of a hand so as to facilitate handling of the crate, thematerial stretched by the perforation serving as an edge 9, said edgeenabling the load of the crate to be distributed on a picking up surfacelarger than the one the sole thickness of the side 5d or 5e wouldgenerate concerning the length of the opening 8.

According to one main preferred embodiment, the assembling of twoprofile sections 7 with one profile section 1 so as to constitute thecrate 5 shown on FIG. 1 is effected by the automated hot glueing of theexternal surface portions 7c and 7d of the borders 7a and 7b onto thecorresponding portions 5f and 5g of the internal surfaces of the sides5b and 5c.

According to one secondary embodiment, the assembling of the two profilesections 7 with one profile section 1 is effected by the ultrasonicwelding of the surface portions 7c and 7d to the portions 5f and 5g.

According to another embodiment, the assembling of the two profilesections 7 one one profile section 1 is effected by stapling the surfaceportions 7c and 7d to the portions 5f and 5g.

By way of non-restrictive example, the following description of thevarious stages for producing plastic crates or other receptacles shallmake it easier to understand the advantages of the method of the presentinvention and appreciate its simplicity.

In one first production phase, the profile 7 is extruded, perforated andtruncated with its sections being stored. Extrusion is effected withconventional extrusion means with a plastic profile, that is with theaid of an extruder provided with a suitable die and a sequence lineincluding a conformation bench, a drawing bench and a cutting orsectioning bench. A hydraulic or pneumatic perforation bench is insertedbetween the conformation bench and the drawing bench and produces theperforations specific to the profile 7.

In a second production phase, the same extrusion line is used as the oneused in the first phase after having replaced the die and the coolingjig so as to be able to produce the profile 1 and, after having modifiedthe punches of the perforation bench, to produce the perforationsspecific to the profile 1.

In a third production phase, two profile sections 7 are assembled with aprofile section 1 on an assembling bench, the feeding of the profilesections 7 being transversal with respect to the feeding of the profilesections 1 and the positioning of the profile sections 7 being effectedafter either the pre-sizing of their external surface portions 7c and 7dor prior to the stapling or ultrasonic welding of the portions 5f and 5gof the profile section 1 onto the portions 7c and 7d according to theselected assembling method.

We claim:
 1. A method for producing plastic crates, each crate includinga bottom, four sides, and four borders for linking the sides,comprising:extruding at least a first and second profile of plasticmaterial, said first profile having a first cross section and saidsecond profile having a second cross section different from said firstcross section, said first and second profiles providing said bottom,four sides and four borders; cutting said profiles into a plurality ofsections; perforating at least one of said sections by punching so as tostretch the plastic material and generate a traction prestressing insaid at least one section; folding said sections of said first profileto form said bottom and two of said sides; and assembling said sectionsof said first and second profiles so as to form said crates; saidsections of said second profile acting as said borders for linking saidsides, said bottom, four sides and four borders of each crate beingformed from assembled sections of said first and second profiles.
 2. Amethod according to claim 1 wherein said second profile is extruded toinclude a hollow triangular form, said hollow triangular form acting asat least one of said borders for linking said sides.
 3. A method forproducing plastic crates, each crate including a bottom, four sides, andfour borders for linking the sides, comprising:extruding at least twoprofiles of a plastic material, said profiles providing said bottom,four sides and four borders; cutting said profiles into a plurality ofsections; perforating at least one of said sections by punching so as tostretch the Plastic material and generate a traction prestressing insaid at least one section; and assembling said sections so as to formsaid crates, wherein the four sides include a first and a second pair ofopposite sides and the crates are obtained by extruding at least onefirst profile adapted to form the bottom and the first pair of oppositesides of each crate, by extruding a second profile adapted to form thesecond pair of opposite sides and the four borders of each crate, and byassembling at least one section of the first profile and two sections ofthe second profile, so as to form one crate.
 4. A method according toclaim 3, wherein said first profile is flat and includes twolongitudinal folding grooves and the crates are obtained by folding saidfirst flat profile along said grooves, before assembling the firstprofile sections and said second profile sections.
 5. A method accordingto claim 3, wherein the crates are obtained by extruding two firstprofiles and by longitudinally juxtaposing and assembling sections ofsaid first profiles, before assembling said assembled first profilesections and said second profile sections.
 6. A method according to anyone of claims 3 to 5, wherein said sections are assembled by gluing. 7.A method according to any one of claims 3 to 5, wherein said sectionsare assembled by ultrasonic welding.
 8. A method according to any one ofclaims 3 to 5, wherein the profiles are successively produced on asingle extrusion line, before assembling said sections.
 9. A methodaccording to claim 3, wherein portions of said sections adapted to formtwo opposite sides of each crate are perforated so as to provideopenings allowing for the passage of a least four fingers of a hand. 10.A method according to claim 3, wherein at least one of said profiles isadapted to form said borders and said border-forming profile is extrudedwith a hollow form, and wherein at least one of said profiles is adaptedto form said bottom and said bottom-forming profile is perforated at atleast one location intended to be in alignment with said hollow formwhen assembling said sections.